PORTLAND – The man who disappeared in the Old Port just days before his graduation from Harvard Business School grew up in a small town in Kansas, where friends said Monday that his disappearance has had a profound impact on a tight-knit community.

Nathan Bihlmaier describes himself on his Twitter page as a “Boston transplant and small town Kansas native.”

He vanished early Sunday after spending Saturday night in the Old Port with two classmates. The three men had come to Portland to celebrate their graduation from Harvard Business School this Thursday.

“We are worried about him. When I went to work this morning, that’s the first thing people started talking about. His family are good people,” said John Girard, who owns Girard’s grocery store in Osborne, Kan.

According to his Facebook page, Bihlmaier grew up in Osborne, a small farming community of about 1,400 people in north central Kansas. He graduated from Osborne High School in 1999.

After graduating, he enrolled at Kansas University. He just completed a two-year program at Harvard Business School, where he was expected to graduate with a masters degree in business administration.

His younger brother, Matt Bihlmaier, contacted Monday night at a relative’s home in Kansas, said the family is not ready to talk to the media.

Friends and acquaintances back in his hometown of Osborne say Bihlmaier’s family is well established and known in the small town.

His parents, Steve and Cheryl Bihlmaier, own and operate Farmer’s Bank in Osborne. His grandfather, Gene Bihlmaier, operates the local State Farm insurance agency.

Girard said Osborne is small town living at its best.

“The closest Walmart is 90 miles away,” he said.

“Osborne is a very close-knit community. Everyone knows everybody,” said Rhonda Landsverk, who taught Bihlmaier how to swim when he was in high school. Bihlmaier worked at the community pool as a lifeguard.

“Right now, I am just sick (with worry). He was such a sweetheart,” Landsverk said.

“He was a very good student. Very smart and very organized,” said a former teacher, Kenny Ubelaker. “He was a pleasant kid to be around.”

Ubelaker, who will retire this week after 33 years in teaching, has lived in Osborne for most of his life. He taught high school classes in government, psychology and world history.

“Nate’s family has been in this town for years. They’ve always been a staple of the community,” Ubelaker said.

When news about his disappearance began to pop up on the Internet and Facebook, the town could not talk about anything else, Ubelaker said.

“When you are a town our size, everything is pretty personal,” he said.

Bihlmaier’s life as a family man and businessman was just beginning. His wife, Nancy, is pregnant with their first child.

And Brian Kenny, a spokesman for Harvard Business School, said the 31-year-old had recently secured a job — as director of Accountable Care Solutions at Optum, a hospital and health care agency in the Greater Boston area.

Kenny said Bihlmaier started a blog in which he wrote about what it meant to be a father for the first time.

“He was thrilled about the prospects of being a new father,” Kenny said.

Staff Writer Dennis Hoey can be contacted at 791-6365 or at: dhoey@pressherald.com